Pipe conveyors are known that use a belt to convey bulk material between the phases of mining, processing, and storage. Unlike the troughed conveyer the pipe conveyor encloses the bulk material during transport, allowing it to be used to transport the bulk material through areas where spillage and dust are major concerns, or in the case of dangerous or hazardous materials.
Known pipe conveyors transport the material in a circular cross-section formed by overlapping belt edges and using idlers arranged in a hexagonal pattern to form a tubular shape. At the loading point these systems provide a trough conveyor for loading of the material. After loading the material, the belt is formed into a pipe shape for the transport length of the system and re-opened at the destination for the unloading of the material in the standard manner of a troughed conveyor. Because the material is enclosed by the belt during transport, spillage, scattering, and flying dust are eliminated, making the pipe conveyor an effective, non-polluting transport system. These systems also allow the pipe conveyor to maneuver both vertical and horizontal curves that would be very difficult to impossible for the conventional conveyor without loss of conveyed materials. Also, because pipe conveyors load and discharge the bulk material in the conventional manner, standard equipment can be used at the head and tail ends, making the system cost effective and efficient.
Pipe conveyor systems of the state-of-the-art, such as in WO 88/09759; EP 0253148; DE 31 45 899; DE 36 20 906; DE 36 24 122; EP 0194509; U.S. Pat. No. 5,080,221; and U.S. Pat. No. 4,723,653 and others, are limited with regard to the angle of inclination of conveyance. In such known prior systems the pipe conveyors transport the bulk materials at an angle of up to 30° and no higher. With previous designs the maximum filling of the pipe conveyor was considered to be 75% of the entire cross-sectional volume of the pipe. This limitation was present because any filling larger than that would result in an unstable running condition which would send the conveyor belts into either a clockwise or counterclockwise turning motion.
DE 196 17 089 discloses a conveyor that has several successively mounted roller frames arranged so that the cross-section enclosed by the conveyor belt when changing over to the rising section is reduced by 15 to 25% compared with the horizontal section previously covered. The conveyor belt, before beginning of the cross section reduction, may receive an oval cross-sectional shape with horizontal centerline. With this a return of the hose belt conveyor is easier and better controllable in the rising distance section. The reduction in cross-section corresponds to the part of the cross-section not covered by material when the belt is loaded in the horizontal section.